Home › Trials › NCT05431088

Phase 2/3 testing of osivelotor in adults and adolescents with sickle cell disease.

A Phase 2/3 Randomized, Multicenter Study of Osivelotor Administered Orally to Adult and Adolescent Participants With Sickle Cell Disease

Phase2; Phase3 Interventional Pfizer · NCT05431088

This trial tests whether an oral medicine called osivelotor can safely reduce pain crises and improve blood measures in people aged 12–65 with sickle cell disease.

Quick facts

PhasePhase2; Phase3
Study typeInterventional
Enrollment389 (estimated)
Ages12 Years and up
SexAll
SponsorPfizer Industry-sponsored
Locations49 sites (New Haven, Connecticut and 48 other locations)
Trial IDNCT05431088 on ClinicalTrials.gov

What this trial studies

This multicenter, Phase 2/3 program gives oral osivelotor to adolescents and adults with sickle cell disease to define an optimal dose, compare efficacy with placebo over 48 weeks, and offer a long-term open-label extension for safety and blood response monitoring. Part A is a dose-finding phase in adults to establish safety, tolerability and pharmacokinetics/pharmacodynamics. Part B randomizes adults and adolescents to osivelotor or placebo to measure clinical outcomes including vaso-occlusive crises over 48 weeks. The Open-Label Extension follows participants who completed Part B to collect longer-term safety and hematologic data.

Who should consider this trial

Good fit: Ideal candidates are people aged 12–65 with sickle cell disease who have had 2 to 10 vaso-occlusive crises in the past year and can keep a stable dose of hydroxyurea or L‑glutamine if they are taking those medicines.

Not a fit: Patients who are pregnant or breastfeeding, receive regular red blood cell transfusions, have had more than 10 crises in the past year, or were recently hospitalized for a vaso-occlusive event are unlikely to qualify or benefit from this protocol.

Why it matters

Potential benefit: If successful, osivelotor could lower the frequency of painful vaso-occlusive crises and improve hemoglobin or other blood measures for people with sickle cell disease.

How similar studies have performed: Other modern sickle cell therapies such as voxelotor (improving hemoglobin) and crizanlizumab (reducing crises) have shown clinical benefits, so this approach builds on prior successful targeted treatments.

Eligibility criteria

Show full inclusion / exclusion criteria 
Inclusion Criteria:

Part A, Part B, and OLE:

* Male or female with SCD
* Participants with stable Hb value as judged by the Investigator
* For participants taking hydroxyurea and/or L-glutamine, the dose must be stable for at least 90 days prior to signing the ICF or assent and with no anticipated need for dose adjustments during the study in the opinion of the Investigator.

Part B:

* Participants with SCD ages 12 to 65 years, inclusive
* Participants with more than or equal to 2 and ≤ 10 VOCs within 12 months of Screening.

OLE:

\- Participants who have completed the Part B will be eligible.

Exclusion Criteria:

Part A, Part B, and OLE:

* Participants who had more than 10 VOC within 12 months of screening
* Female participant who is breastfeeding or pregnant
* Participants who receive RBC transfusion therapy regularly or received an RBC transfusion ---for any reason within 90 days of Day 1
* Participants hospitalized for sickle cell crisis or other vaso-occlusive event within 14 days of signing the ICF or anytime during the screening period.

Where this trial is running

New Haven, Connecticut and 48 other locations

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
View on ClinicalTrials.gov → Find more trials like this →
Conditions Sickle Cell Disease
Last reviewed 2026-06-13 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.